Transformer circuit



Sept. 19, 1944. A. N. GARIN 2,358,631

TRANSFORMER CIRCUIT Filed NOV. 23, 1942 COIL 5/1/70 6 ON ANOTHER cons LE6 COIL 3 14/1/04 am 5 ONE CORE [.56

Inventor: Alexis N. Garin,

by y mW/ H IS Att obney Patented Sept. 19, 1944 TRANSFORMER CIRCUIT Alexis N. Garin, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application November 23, 1942, Serial No. 466,559

9 Claims.

This invention relates to transformer circuits and more particularly to improvements in loadratio-control circuits.

By load-ratio-control" is meant the control or variation in the turn ratio of a transformer while it is under load and without interrupting the load current. This is usually accomplished by means of a plurality of taps in one of the transformer windings combined with switching mechanism for changing tap connections without interrupting the load current.

The maximum kva which a single loadratio-control switching mechanism can safely handle is less than the maximum kva which the largest power transformer can carry continuously and therefore it is the switching mechanism which limits the maximum kva.

In accordance with the present invention there is provided a novel and simple arrangement whereby the transformer kva is divided between a plurality of load-ratio-control switches so as substantially to increase the amount of kva which the load-ratio-control transformer can carry.

An object of the invention is to provide a new and improved transformer circuit.

Another object of the invention is to provide a new and improved load-ratio-control circuit.

A further object of the invention is to provide a novel combination of a single-phase transformer and a three-phase load-ratio-control mechanism.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the single figure of the eecompanying drawing, wherein I have illustrated diagrammatically a preferred embodiment of the invention, the transformer is a single-phase twolegged core type concentric winding transformer I and the load-ratio-control mechanism is a standard three-phase mechanism 2. Only one of the transformer windings is shown and this winding may be either the primary winding or the secondary winding or the high voltage winding or the low voltage winding. It is shown as comprising four coils 3, 4, 5 and 6, the coils 3 and 4 being mounted on one leg and the coils 5 and 6 being mounted on the other leg, it being understood that the coils 3 and 4 taken together are concentric with a coil of the other transformer winding or windings (not shown) and similarly the coils 5 and 6 are concentric with the remaining coil of said other winding of the transformer.

Each of the four coils has the same number of turns and they are provided with similar sets of taps. All four coils are connected in parallel with each other across a circuit 1.

The ratio adjuster 2 comprises three similar switching mechanisms 8, 9 and In all driven in unison by a common operating mechanism H. These switching mechanisms may be of any wellknown type and are shown by way of example as being of the double-finger mid-tapped reactor type in which each switching mechanism has two non-arcing duty ratio adjusting contact fingers I2, two arcing duty contactors l3 and a mid tapped reactor Hi. The ratio adjuster 8 is connected in circuit with the coil 5, the ratio adjuster I0 is connected in circuit with the coil 3, and the ratio adjuster 9 is connected in circuit with the coils 4 and B in parallel, that is to say, the latter ratio adjuster carries the sum of the currents of the coils 4 and 6.

In order to provide equal division of load current in the three ratio adjusters the axial length of the coil 4 is made equal to one-third the combined axial length of the coils 3 and 4 and similarly the axial length of the, coil 6 is made equal to one-third the combined axial length of the coils 5 and 6. This crowding of the turns of the coils 4 and 5 together with respect to the spacing of the turns in the windings 3 and 5 so alters the reactance relationships of the windings that one-third of the total current in circuit 1 will flow in winding 3, one-third will flow in winding 5, one-sixth will flow in winding 4 and one-sixth will flow in winding 6. Therefore, as the ratio adjuster 9 carries the sum of the currents in the windings 4 and 6, it will carry the same current as is carried by the ratio adjusters 8 and i0.

Operation of the driving mechanism I l for the ratio adjusters will cause these adjusters to go through their standard cycle of operation in unison so that the operating mechanism may be stopped at any point in the cycle without disturbing the current division between the coils and ratio adjusters.

While the invention is not limited to the particular arrangement shown in which a singlephase transformer is combined with a threephase ratio adjuster, it will be seen that this particular combination is quite practical because three-phase ratio adjusters are standard mechanisms, so that by using the largest size threephase adjuster the current capacity of a singlephase load-ratio-control transformer may be tripled. However, by using diflerent numbers of coils or different numbers of switching mechanisms or different connections between them, the kva capacity of load-ratio-control transformers,

' especially single-phase transformers, may be inall such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a transformer winding having a plurality of parallel-connected multitapped coils, separate load-ratio-control switching mechanisms for respectively making selective connection with the taps of said coils so as to vary their efiective turns, and means for operating said load-ratio-control switching mechanisms in unison so as to maintain equality between the effective turns of said coils, said coils having a predetermined reactance relationship for causing a predetermined division of load current between them.

2. The combination, as in claim 1, in which said coils have different physical dimensions and said load current division is equal.

3. The combination, as in claim 1, in which said winding is distributed symmetrically on both legs of a core-type single-phase transformer, said coils are four in number, and said load-ratio-control switching mechanisms are three in number.

4. A single-phase two-legged core concentric winding type transformer having, in combination, four multi-tapped coils of the same number of turns, two of said coils being on one core leg and two on the other, all of said coils being connected in parallel, a three-phase load-ratio adjuster having three mechanically interconnected tap-changing switching mechanisms, two of said switching mechanisms being connected respectively to the taps of two of said coils which are on different core legs, the remaining ratio adjuster being connected to the taps of both of the remaining coils, said remaining coils having an axial length which is one-half the axial length of the other coils.

5. The combination, as in claim 4, in which the coils on each leg are mounted side by side with the axial length of each said remaining coils being one-third the combined axial length of the two coils on each leg.

6. In combination, a transformer having a plurality of windings whose voltages are in phase with each other and whose currents are in phase with each other, a plurality of complete loadratio-control mechanisms, means for connecting said mechanisms to said transformer so that the kva of said transformer is equally divided between said mechanisms, and means for operating said mechanisms in unison.

7. In combination, a transformer having a plurality of windings whose voltages are in phase with each other and whose currents are in phase with each other. a plurality of load-ratiocontrol mechanisms, means for operating said mechanism in unison, and means for connecting said mechanisms to said transformer so that the kva of said transformer is divided between said mechanisms in a predetermined ratio.

8. In combination, a single'phase transformer, a plurality of duplicate load-ratio-control mechanisms, means for connecting said mechanisms to said transformer so that they divide its kva between them in a predetermined proportion, and means for operating said mechanism in unison.

9. In combination, a single phase transformer, a plurality of load-ratio-control mechanisms, means for operating said mechanism in unison, and means for connecting said mechanisms to said transformer so that they divide its kva between them in a predetermined proportion.

ALEXIS N. GARIN. 

